Roscosmos gave recently more details regarding not successful launch attempt of Soyuz-2.1A with Progress MS-07 performed on October 12, 2017 at Baikonur Cosmodrome.
To remind whole situation: Progress MS-07 first launch attempt took place on October 12, 2017 from Launch Site 31/6 at Baikonur Cosmodrome at 09:32 UTC. Unfortunately seconds before ignition of the main engine second umbilical connection failed to retract and launch was scrubbed just before liftoff. Roscosmos performed another attempt two days later at 08:47 UTC.
Reasons for surprising scrub was announced three days later. According to quoted by TASS Executive Director for Manned Space Flights at the State Space Corporation Roscosmos Sergei Krikalyov, problems with launch had source in micro-computer glitch. Unfortunately still it is not perfectly clear why problem appeared. As Sergei Krikalyov claims:
"The root cause still has to be studied but we have identified the equipment. A valve did not open in it and we understood that a glitch occurred in the control system, in one of micro-computers and we replaced it. Why didn’t the computer send the signal? This was either a failure of electronics or a failure of the software,"
Roscosmos failed to fully evaluate what caused the problem and still potential solution preventing from such situations in future is not known. A government commission is investigating the problem and probably until next mission of Progress on the top of the Soyuz accident will be already explained.